Adeno-associated virus (AAV), a member of the Parvovirus family, is a small nonenveloped, icosahedral virus with single-stranded linear DNA genomes of 4.7 kilobases (kb) to 6 kb. AAV is assigned to the genus, Dependovirus, because the virus was discovered as a contaminant in purified adenovirus stocks. AAV's life cycle includes a latent phase at which AAV genomes, after infection, are site specifically integrated into host chromosomes and an infectious phase in which, following either adenovirus or herpes simplex virus infection, the integrated genomes are subsequently rescued, replicated, and packaged into infectious viruses. The properties of non-pathogenicity, broad host range of infectivity, including non-dividing cells, and potential site-specific chromosomal integration make AAV an attractive tool for gene transfer.
AAV vectors have been described for use as delivery vehicles for both therapeutic and immunogenic molecules. To date, there have been several different well-characterized AAVs isolated from human or non-human primates (NHP).
Recently, investigators have described a large number of AAVs of different sequences [G. Gao, et al., Proc Natl Acad Sci USA, 100(10):6081-6086 (May 13, 2003); US-2003-0138772-A1 (Jul. 24, 2003)] and characterized these AAVs into different serotypes and clades [G. Gao, et al., J. Virol., 78(12):6381-6388 (June 2004); International Patent Publication No. WO 2005/033321]. It has been reported that different AAVs exhibit different transfection efficiencies, and also exhibit tropism for different cells or tissues.
What is desirable are AAV-based constructs for delivery of heterologous molecules to different cell types.